This section provides background information related to the present disclosure which is not necessarily prior art.
Vehicle suspension rods and in particular torque rod assemblies are used in the transportation industry to stabilize vehicle axles relative to a vehicle frame. A typical torque rod assembly comprises a rod or a link with connectors attached at each end. The designs for the connectors vary, but prior art designs have included ball studs, metal tubes and straddle bars. In a typical application, one end of the torque rod assembly is connected to a vehicle frame or other supporting member and the other end is connected to an axle or other component of the vehicle. The torque rod connectors usually permit rotation or pivoting of the connecting rod or link in several planes and these connectors are often isolated from shock with elastomeric bushings. The torque rod assemblies have been mounted parallel to, at an angle to or perpendicular to the vehicle axle. There are some designs where the torque rod assemblies are mounted in a transverse or “V” pattern relative to the vehicle axle. In all of the above designs, the torque rod assemblies prevent the axles or other components from rotating about their own axis, from moving for-and-aft, and from moving laterally.
Due to the severe loadings on torque rod assemblies, these assemblies have traditionally been manufactured from steel rods, steel tubing, forgings and castings. These components, once produced, are welded together using MIG, TIG or some other type of surface welding technique. The current manufacturing methods for these assemblies are costly with a large portion of the costs being associated with the machining of the raw forgings or castings in order to permit the assembly of the bushings and the connectors.
Steel stampings have been considered for this application. However, the end configurations required to support the torque rod connectors have proven to be difficult to form.
Recently, attempts have been made to manufacture torque rod assemblies using composite materials and molded polymers for the connecting rod or link. These types of torque rod assemblies have a variety of disadvantages. For example, the materials are generally not strong enough to withstand the variety of loadings to which they are subjected. In some cases, the material is not rigid enough to provide the stability required on the vehicle. Some materials are subject to impact damage, as one would expect from a gravel road. Some of the molded torque rod assemblies which have adequate strength are too bulky to fit the particular application. Finally, some molded torque rod assemblies are simply too expensive.
More recently, torque rod assemblies have been designed using a stamped steel metal reinforcement plate having a pair of flange reinforced bores located at each end of the plate. The reinforcement plate is encased within a polymer shell with the shell being of a different material than the reinforcement plate. The encasing of the reinforcement plate within the polymer shell eliminates the need for machining the ends of the torque rods as well as any need to weld the torque rods. While these torque rod assemblies have proven to be useful in some applications, due to the stamped metal plate only being a reinforcement plate, the maximum loading for these hybrid torque rod assemblies is limited.